Luca Netz, the CEO of Web3 NFT community Pudgy Penguins, has fallen into the trap many financial experts warn against: buying a new, fancy car. And he very much regrets it.

Netz became a self-made millionaire at age 18 after selling his e-commerce faux-gold jewelry business. He went on to buy Pudgy Penguins for $2.5 million, recently overseeing the launch of the brand’s plush toy offshoot at Walmart. Today the 25-year-old estimates he’s worth over $100 million.

While he never went down a spending rabbit hole the way his wealthy peers have, he told Fortune in a recent interview, he did admit to an uncharacteristically flashy purchase: a Rolls-Royce Cullinan. That’s an SUV with leather seats and a retractable roof—and a starting price of over $375,000 for the 2023 model.

There’s “no purchase that I regret more than my Rolls-Royce Cullinan, which is easily the worst car I’ve ever owned,” Netz said. “It’s a great car on its face. But it’s big and clunky—I call it the oil rig. It has no gadgets and no functionality. Outside of the pretty orange interior I have, it serves no purpose.”

When asked if he has plans to sell it, he joked: “It’s gonna stay an oil rig in the front lawn of my home just in case we strike gold one of these days and I need to start pumping oil. Maybe that thing can do that.”

Perhaps Netz regrets the purchase so much because he’s so hesitant to spend substantial money on any luxuries at all—a mentality he developed while growing up homeless. He says those years of bouncing around impressed upon him the value of frugality, hard work, and avoiding needless purchases.

“Growing up poor gave me an understanding of the value of a dollar; that’s something that I’ve never lost track of,” he said. “I understand what it is to make $1, to spend $1. And I understand the difference between having $1,000 and not having it.”

Healthy indulgences

Netz’s first major purchase, at 19, was a million-dollar home. He largely remained frugal otherwise, he said, finally beginning to spend when he began socializing with the flashy, sceney L.A. social set.

“I was with some pretty prominent figures, and I felt really left out because I was wearing Dickies and a Gildan T-shirt,” he recalled. “It wasn’t until I felt like a wallflower that I decided to spend some of the money. But I never went down the rabbit hole that others did, where they blew all the money they made.”

He purchased a 2019 BMW M4, to be exact, which was his “favorite car at the time.” Then he slowly eased into lifestyle creep, indulging in “some sneakers, some watches, and some nice attire,” but he says he never went overboard. “BMWs instead of Ferraris. And instead of Louis Vuitton, Theory.”

Netz doesn’t even like to eat at restaurants. “Expensive dinners are a waste of money, because once you eat it, it’s gone, and there’s nothing left to enjoy,” he said. “I think good food is important, but I am not a firm believer in $1,000 steaks, or gold flakes on your steak.”

No wonder he feels the Rolls-Royce was such a mistake, a rare financial misstep for the young workaholic. Self-made millionaire and author David Bach once said that buying a new car is “the single worst financial decision”—and the habits of several billionaires show they agree. Famously frugal Warren Buffett held on to a 2006 Cadillac DTS for some time, and both Mark Zuckerberg and Jeff Bezos have been spotted driving Hondas.

Netz isn’t the only CEO to regret buying a fancy car (and that’s before accounting for the gas mileage). Earlier this year, Chris Nassetta, the CEO of Hilton Hotels, said buying a Porsche was his worst-ever financial decision and “nearly broke” him.

But for the most part, Rolls-Royce excluded, Netz says, he tries not to keep up with the Joneses: “The Joneses’ life is not as good as you think it is.”